Hello everyone, I own a 2012 is with 120k miles. My issue is that my brake pedal feels inconsistent. What I mean by that is that it’s stiffer at times and then randomly gets softer without any noticeable cause or reason. I did a brake fluid flush about 1500 miles ago, and this is where the issue started. I’m probably due for a brake job as well, but was wondering if this sounds like i let air in the system, or if it could be related to my rotors and pads, or if it could be something else altogether. Any help is appreciated thanks!

 

You need to start with a solid bleeding on all four calipers starting with the farthest and ending with the closest. For LHD cars, start pax rear, then driver rear, then pax front, then driver front. If there is any air in the fluid, it will cause inconsistent feel. Fluid changes are recommended annually by Lexus in the standard services at the dealership. There are threads here about brake fluid and we all have our personal preferences. If you're not doing track days/weekends with the car, the fluid isn't a big deal because your brakes never get really hot with street driving.

There is also a known issue with service life on the brake booster and check valve. Ordinarily, this won't cause inconsistent feel during operation, but will make for a very hard pedal when starting. It also leaks unmetered air into the engine and can cause drivability issues especially idle stability issues. If the booster is leaking (worn out) you'll have a hard pedal on start up that sinks quickly once the engine is running. Replacing the booster is not a task for an inexperienced mechanic. The ABS/VSC unit has to be removed to get the booster out, so you've got to disconnect all the brake lines from it, and when you install the booster, you'll need to bleed the master cylinder first, then connect all the lines again and do a complete system bleed. It's not terribly difficult if you have brake system experience, but this is the thing stopping your car so you really want to be sure you do it correctly. It could be a life or death issue if you get it wrong.

 

I’m not having those issues on my car specifically with the pedal being hard on start up and the pedal doesn’t sink, the travel feels the same just the pressure needed to compress varies. So I think your right need to flush them again.